Typically you will edit your local files and then use the publishing tools to upload them to your server, but it is also possible to edit remote files directly on the server in Espresso. To do so, select the server you wish to work with in the PUBLISH section of the sidebar, select list or column mode in the "View" button group in the toolbar, and click the "Browse" button.
Once you are connected, double click any text file to edit it in Espresso, or any other file to open it in the default program associated with that file type. (See browsing servers for more info.)
Remote files open in your workspace will have a icon next to them when you select them, and any changes you make to them will be immediately uploaded to the server when you save. Remote files will not be automatically re-opened when you relaunch a project because they are saved locally in a temporary cache.